The F-35 will take aircraft support to a new level. Imagine, for example, a combat aircraft that requires no complex troubleshooting equipment at the flight line or a logistics system that will automatically locate the appropriate technician for a parts replacement.
The F-35’s support system is still in its infancy and many decisions remain to be made before the aircraft is fielded. But the concepts surrounding Joint Strike Fighter (JSF) support can well be described as revolutionary. They include:
An unprecedented level of onboard diagnostics and prognostics,
A highly automated logistics information system,
Eliminating the need for most intermediate-level support, and
More compact and efficient automatic test equipment (ATE) that may share diagnostics data.
It all fits into the quest by military customers for faster, cheaper and simpler aircraft support.
JSF ATE
The JSF’s ATE suite, called LM-Star, is described as one tester, available in three configurations: "basic," electro-optic and RF (radio frequency). Its footprint is small, compared with the F-16, which involves multiple types of ATE for intermediate (I-level) maintenance and at least six types at the depot level, says Steve Karlovic, director of standard support systems for Lockheed Martin Information Systems.
The "biggest pro" of LM-Star is affordability, says Air Force Lt. Col. Gene Mittuch, JSF Support Systems IPT (integrated product team) lead at the JSF program office. "The ATE used to develop the avionics can be transferred to the depot and used to run that piece of avionics. You’re gaining affordability by a single set [of ATE] built in greater quantities."
"Industry repair centers will look like military repair centers," adds Jeff Zimmerman, vice president of support solutions at Lockheed Martin Information Systems. So the government can make decisions whether it is more cost-effective or timely to send a box to a Lockheed Martin repair center or a government facility. The company, however, is not now under contract for depot support.
Lockheed has begun to ship its "basic" LM-Star system to suppliers for test program set (TPS) development and component test. The LM-Star architecture is based on that of the U.S. Navy’s and Marine Corps’ Consolidated Automated Support System (CASS) and Reconfigurable Transportable CASS (RTCASS) general-purpose testers, says Tom Dabney, Support Equipment Sub-IPT lead. Its open architecture aligns with the standards of the Defense Department Executive Agent for Automatic Test Systems and the technologies developed by the joint-service NxTest (Next-generation Test) group. Lockheed Martin also emphasizes "harmonization" of JSF test software with CASS and RTCASS, so that TPS software developed for LM-Star eventually will be able to run on this equipment.
LM-Star’s dual software runtime environment allows it to run older Atlas test programs (using TYX Corp.’s PAWS software) and test programs developed using National Instruments’ LabWindows/CVI and TestStand products. JSF partner BAE Systems has provided extensions to TestStand that will improve TPS standardization.
Two-Level Maintenance
The two-level, government/contractor maintenance concept–known as organizational-to-depot, or "O-to-D"–could reduce or eliminate the need for JSF I-level avionics and engine support, according to the program office. The highly automated worldwide logistics network, backed by high-reliability components, the thinking goes, could deliver parts more rapidly than they could be repaired on an I-level bench.
Lockheed Martin further envisions a 40 to 50 percent savings in manpower and infrastructure costs at the unit (e.g., wing) level, says Mittuch. (Units, in this context, include both intermediate-level shops and flight line maintenance.) As the Air Force’s fleet of F-16s is retired, for example, "not having I-level maintenance is a huge logistics footprint [savings]." But life-cycle cost estimates, he cautions, are still very preliminary and won’t become firmer until the design is more mature.
Lockheed also has proposed a "power-by-the-hour" type of logistics support, Mittuch says. The details of such an arrangement, under which the military would not have to own all the spares, remain to be worked out. This commercial practice, which adds long-term predictability to maintenance cost calculations and boosts incentives to reduce costs and increase efficiency, would be new to fighter aircraft and large military fleets. Another implication of contractor-owned spares could be that the services would not be authorized to work on black boxes in the field, Mittuch says.
Ideally, the concept would apply to all F-35s, to achieve maximum benefit, but each partner will have to make its decision, based on its country’s needs and legal requirements. A two-year company study (due in 2004) will determine whether these ideas are cost-effective.
The support concept also envisions the JSF ATE’s use of current and historical built-in test (BIT) information, something that is not done today. ATE-based reasoning processes could use the information in a rules-based environment, improving ATE runtimes and diagnostic accuracy.
Onboard diagnostics information, by the same token, would reduce the ATE workload, compared with legacy support programs. Fewer healthy components would be removed at the flight line because of limited BIT and diagnostics capabilities.
Minutes of Down Time
"The maintenance concept takes advantage of data collection on the aircraft, with real-time downlinks to the ground and much more rapid prepositioning of parts, people and processes, in order to turn the aircraft back around much quicker than conventional aircraft are today," says Zimmerman.
Integrated combat turn (ICT) time–how fast you can get an aircraft back in the air–is key. A legacy aircraft can take "hours and hours to turn around–if you’ve got all the parts. But the JSF is going to be measured in minutes," Zimmerman says. The onboard prognostics and health management (PHM) system’s ability to transmit fault data back to the aircraft’s base or ship before landing will be crucial.
Sortie generation rate is a related requirement. Currently, Navy and Air Force JSF variants must accommodate three sorties per day, and short takeoff and vertical landing (STOVL) versions for the Marine Corps and the UK must provide four sorties per day.
If the PHM system advances as expected by the 2008-2009 period, it will be revolutionary, Mittuch states. Maintenance could be scheduled around the time parts are predicted to fail, rather than after they have failed, a potentially huge savings in operations and support (O&S) costs. O&S costs for the F-35 fleet over its life cycle must be half that of conventional fighter aircraft, according to Lockheed Martin. The major contributors to these savings are the high-reliability avionics and the PHM capability of the logistics information system.
Employing Artificial Intelligence (AI)
Intelligent PHM software processes hosted in the JSF’s integrated core processor will constantly monitor internal test and parametric information from aircraft subsystems, explains Greg Brown, Lockheed Martin Aeronautics’ air system specialty engineering team lead. PHM software also will perform prognostics functions, predicting when components will fail, so that equipment is not replaced prematurely. This tiered structure of higher intelligence engines then "reasons on the data and determines whether the systems reporting problems are giving false information."
If you can better isolate a fault on an aircraft, "you can put the logistics infrastructure in motion before you land," reducing spares and manpower requirements, Brown explains. The cost of training technicians also could be reduced.
Legacy aircraft, equipped with only BIT and offboard processes to evaluate BIT data, also tend to have high false alarm rates, he says. "You may pull the wrong component out," which then has to be checked.
As the PHM and logistics information systems will not mature until later this decade and will continue to evolve long after that, designers have emphasized flexible architectures that can adopt the most current information technologies over time.
The F-22 has some "area managers"–software modules that monitor BIT data from specific systems–but not a tiered architecture with a higher-level reasoning engine to arbitrate between conflicting reports. The F-35’s higher-level manager will use AI techniques such as model-based reasoning, neural networks and fuzzy logic to eliminate false alarms and isolate faults. PHM software will compose about 10 percent of the aircraft’s total code. Up to 1 gigabyte per flight of fault and "life usage" information can be stored on board.
The PHM architecture includes five area managers:
- Vehicle systems–monitors flight controls and utility subsystem, including landing gear, environmental control system and external lighting;
- Mission systems–monitors communications, navigation, electronic warfare and stores management gear;
- Airframe–monitors sensors to assess the health of the aircraft structure, measuring airframe stress, G-force exceedances, and life usage;
- Propulsion–monitors engine and lift fan health; and
- Air vehicle–cross-correlates BIT failure information across all systems for "failure corroboration" and fault isolation.
Fault information will be data-linked to the ground and fed not only into the logistics system, but also to systems supporting operations. Thus, if there has been a major failure like an engine outage, the operators will know that the aircraft "may need to be resequenced in the sortie cycle," Brown says.
Because of the F-35’s extensive onboard diagnostics, the goal is to have no troubleshooting equipment at the flight line–just a maintainer with spares and basic support equipment. A maintenance interface panel, currently planned for the right side of the fuselage, will allow data to be downloaded to a portable maintenance aid via wired, wireless or optical fiber link. The division of labor between the maintenance panel and the portable device has not yet been determined.
PHM processes are expected to isolate faults to the board level in the avionics systems and to line replaceable components (LRCs), such as hydraulic actuators and gearboxes, on the mechanical side. The JSF will have a "much higher level of mechanical isolation," Brown says, because of the use of electronic controllers to observe failures in those systems.
ALIS: Total Asset Visibility
The concept also depends on the Autonomic (self-running) Logistics Information System (ALIS). Downlinked fault data, along with failure codes and information about consumables to be replaced, such as fuel and stores, will trigger the ALIS. ALIS, in turn, will determine the type of problem (e.g., electrical or mechanical), locate a properly trained technician–based on stored training records–and start the process of pulling parts from stock.
ALIS is designed to provide "total asset visibility," says Doug Bowman, director of logistics information technology solutions, with Lockheed Martin Information Systems. Ideally, the support management software will serve as the "repository and archive of each airplane," tracking every component from design to end of life. Based on current and expected software technologies, ALIS will generate work orders and provide access to tech manuals and repair procedures. It will aid operators to select the best pilot for a mission by storing pilot training records. The system will function not only as a data warehouse, but also as a decision support tool, workflow manager, maintenance scheduler, resource allocator and an aircraft software distribution mechanism.
"The autonomic logistics system is like the autonomic nervous system," Karlovic says. "The heart beats and you do a lot of things without thinking about it. There needs to be a fair amount of intelligence."
Determining Life Expectancy
ALIS also will perform "life usage calculations," measuring the remaining life of aircraft structure and components, based on PHM data. It will employ trend analysis and forecasting algorithms that will look at the environment in which the components are used, the failures over time, and the required maintenance, refining predictive models.
A minimal deployable unit (MDU), or ALIS subset, also is planned for forces in offshore deployments where there may be insufficient bandwidth for connectivity to the full logistics information system. Afterwards MDU inputs would be synchronized with the main ALIS system.
Lockheed Martin has completed Build 1 of the ALIS Test Failure Resolution Report component. Suppliers will enter part failure information and root cause analysis into this system, starting in the design and development phases, which will help improve parts reliability in later upgrades.
Going into the flight test period in 2005-2006, ALIS will have basic parts ordering and digital technical data generation features, Mittuch says. By around 2010, he expects ALIS to be interfaced to the aircraft, able to download PHM data and to be tied to customer support centers.
Agile Rapid Global Support
Future automatic test equipment (ATE) also will borrow ideas from a research program called ARGCS, for Agile Rapid Global Combat Support (ARGCS) system. Led by the U.S. Defense Department (DoD) Executive Agent for Automatic Test Systems (ATS), ARGCS aims not only to demonstrate new technologies, but to prove the concept of interservice test software interoperability.
"The ACTD gears at making an open system architecture that will allow TPSs [test program sets] to be easily rehosted," explains Jay Romania, the Army ATE lead, at the TACOM (Tank-Automotive and Armaments Command) ATE/TPS Center, which also manages aviation support. "So, in a theater of battle, you could have an Army tester repair a Joint Strike Fighter [component] because you would be able to recompile the TPS on it and run it."
ARGCS has been proposed as an advanced concept technology demonstration (ACTD) to emphasize the effort’s joint aspect and obtain DoD funding, says Bill Ross, assistant director of the Defense Department’s ATS Executive Agent Office. A decision on the ACTD was expected in March, but the project will proceed elsewhere if ACTD funding is unavailable, he says.
ACTD planning and design could begin this fall and hardware and software integration, in February 2004, upon the selection of an ARGCS integrator, probably by a competitive process. So far, the Navy, Marine Corps and Army are involved with ATS demonstrations. Post-ACTD production of equipment, at the discretion of the individual services, could begin in 2006.
The ARGCS system-level demo will involve lower-level technologies already demonstrated through the joint-service NxTest (Next-generation Test) team, such as multi-analog test, synthetic instruments, bus emulation and XML (extensible markup language) for test, a flexible means to share formats and data. Planners also expect ARGCS to demonstrate the reuse of weapon system-level built-in test (BIT) information and historical system failure data to improve the quality of the diagnostics, Ross says.
The Army could participate in the ACTD with "Version 6" (V6) of its Integrated Family of Test Equipment (IFTE), which will combine testing for ground equipment, such as the M1 tank and Bradley fighting vehicle, and avionics for the Apache and the Kiowa Warrior helicopters, in a small footprint.
ARGCS also is pushing toward multirole test equipment to reduce the logistics tail, says Steve Fairbanks, product marketing manager with Teradyne, a test equipment company. Another thrust is knowledge transportability, he says. ARGCS is trying to bridge the gap, from a logistics point of view, between factory, depot, intermediate and operational levels of maintenance, and, as a minimum, to share data among them. It’s hoped that ACTD concepts, once proven, will influence the services’ ATE evolution toward greater ATS interoperability and reduced ownership cost.
ARGCS also will demonstrate the use of multiple runtime systems, which will, for example, allow a tester to run both Consolidated Automated Support System (CASS) and IFTE TPSs, which are written in different programming languages. The Navy has taken a step in that direction already, enabling CASS to run TPSs written in C for the F/A-18 aircraft. The demonstration program also may require hardware adaptation to connect a service’s avionics components, using existing TPSs, to a different service’s tester.
U.S. Navy’s JETI
Commercial off-the-shelf- (COTS) based automatic test equipment (ATE) is changing the way the U.S. Navy conducts shipboard aircraft engine test. The service has deployed the first JETI (Jet Engine Test Instrumentation) system on the aircraft carrier, USS Abraham Lincoln, for intermediate-level test of gas turbine engines. This includes control and monitoring of engines equipped with full authority digital engine controls (FADECs) and monitoring of engine vibration, speed, temperature and pressure. Developed by Racal Instruments, the open architecture system–based on the VXI- and PXI-standard cards–replaces a manual configuration of specialty gauges.
JETI covers the F/A-18E/F, A/B and C/D and the F-14D, EA-6B and S-3A aircraft. Racal provides the chassis, switching and test program sets, with additional components from Agilent, North Atlantic Industries, MacPanel, Trig-Tek and Systran, among others. The Navy has fielded six preproduction JETI units, including four carrier-based and two land-based systems. Racal is preparing an additional two units and expects to supply more in the near future. It also is building a smaller prototype unit based on the same architecture for testing U.S. Marine Corps helicopter engines.
ATE for Design Evaluation
National Instruments (NI) is supplying gear typically associated with back-end test to help evaluate Joint Strike Fighter designs. Lockheed Martin Aeronautics is employing NI’s LabView software development environment and standard PXI instruments to test an engine inlet valve design, using a one-ninth-scale model in a wind tunnel.
The software performs 450,000 floating-point calculations every 50 milliseconds, measuring air pressures across 128 channels at up to 20,000 samples per second. Built by G Systems, the tester uses two PXI chassis, each with eight NI 24-bit dynamic signal acquisition modules.
The data acquisition system provides Lockheed Martin a "much richer set of data to make decisions off of," says Shawn Liu, NI software product manager. This quantity of real world data helps design simulations account for the smallest dynamic characteristics.
Lockheed also employs NI LabWindows/CVI software and measurement hardware to evaluate F-35 subsystems, using a full-scale mockup. The tester uses NI’s ANSI C compiler to simulate an aircraft system and run a subsystem under typical operational sequences and failure scenarios, while monitoring subsystem components.
The NI tester monitors 1,200 signals from the aircraft simulator, using 800 analog and 400 digital inputs and outputs. Data is synchronized via the IRIG-B timing standard.